RU2585707C2 - Polymer strapping tape for banding multiple one or more objects and method of making same - Google Patents

Abstract

FIELD: manufacturing technology.

SUBSTANCE: invention relates to polymer strapping tape for strapping of one or several objects. Polymer strapping tape contains the following components: a) up to approximately 90 wt% of polyester, b) from approximately 1 to approximately 5 wt% of polyolefin; c) from approximately 5 to about 10 wt% of fibrous material.

EFFECT: production of polymer strap.

10 cl, 1 dwg

Description

The invention relates to a polymer strapping tape for tying one or more objects.

Previously, strapping tapes were made mainly of steel and served, for example, for combining metal rolls, fixing packaging items on a pallet (pallet), etc. Along with such steel strapping tapes, in practical conditions, polymer strapping tapes are increasingly being used.

Thus, the application DE 1529995 describes a high tension stretch tape, which consists of a homogeneous extruded axially oriented polymer material. Such polymer strapping tapes are more preferable in comparison with steel strapping tapes, since there is no cut of the corresponding packaging and the ends can be connected in a simple way, using, for example, friction welding. However, polymer strapping tapes are not suitable for high temperatures.

A thermal weld is described inter alia in DE 4007560 A1. In addition, this document addresses the fundamental possibility of cutting individual polymer strapping tapes from a polymeric material for the manufacture of strapping ribbons. To this end, a polymer material for the manufacture of strapping tapes is made as a film material, cut into tapes and then subjected to drawing in order to achieve planar alignment of the micromolecular chains.

In addition, it is possible, of course, to manufacture the polymer strapping tape directly by extrusion, as described, for example, in WO 03/087200 A1. Accordingly, this document provides a polymer strapping tape that consists essentially of polyester and a chemically unmodified polyolefin. Due to this, the strapping made in this way should have increased strength with respect to splitting in the longitudinal direction.

However, the previously described effect is associated with the disadvantage that the temperature stability of the known polymer strapping tape is deteriorated in a known manner. This should be explained by mixing a polyolefin, for example polypropylene, with the main component, the polyester. This is because the melting point of the polyester is in the range of about 270 ° C, while for polypropylene melting points of about 130 ° C are observed. Therefore, the known polymer cladding tape cannot be used for tying objects that, in the process of tying, have a temperature lying in the above range. In addition, when using the known polymer strapping tape, the following disadvantage arises, expressed in the need to match the temperature of previously used welding tongs for connecting the ends, which reduces the suitability of the problematic tape for the client or user.

The strapping tape is also known from JP 11-245290 A. In fact, the problematic strapping tape is made from raw materials that contain polyester in an amount of 60% by weight or more. Additionally, elastomers can be added, such as, for example, polyolefins, namely in a weight fraction of one to 20 parts. In addition, mention is made of the additional addition of, for example, flame retardants, stabilizing agents, coloring agents, and the like. These measures, however, in no way alter the temperature stability and strength, as before, insufficient for certain applications.

In the framework of the application GB 1,132,060 a polymer strapping tape is described for which, among other things, the goal is to increase tensile strength. This applies, however, to extruded film tapes, from which individual strapping tapes are then cut. To this end, application GB 1,132,060, in the case of a polyolefin-based polymer tape, provides for the use of 1 to 30 wt.% Fibrous material relative to the total weight. In this case, the fibrous material is oriented in the longitudinal direction. This kind of approach cannot be implemented in the production of material of individual tapes already for the reason that the width of such individual tapes is typically from 20 to 30 mm with a thickness of up to 1 mm or up to 1.5 mm.

Not to mention the fact that the manufacture of individual strips of film or film tape in accordance with the application GB 1,132,060 is already so unprofitable that the film tape can hardly be made with the same throughout the thickness of the material. In addition, you should be careful not to heterogeneity when introducing fibers. If possible, the constant thickness of the material is, however, of particular importance to ensure the possibility of reliable connection between the ends of the polymer tape. For this purpose, they usually resort to the use of already specified welding tongues or welding tongs and, thereby, to the polymer welding process or work with the joint by friction welding. In both cases, fluctuations in the thickness of the material of the manufactured individual strips lead to the fact that in the circuit region they are not connected to each other over the entire area, as a result of which a break in the connection is possible.

The basis of the invention is the technical problem, which consists in providing this kind of polymer strapping tape, which differs in comparison with the prior art by increased temperature stability and at the same time as high strength as possible. In addition, it should be possible to make the strapping tape as stable as possible with respect to size, so that the connection can also be made with strength increased compared to the previous approach.

To solve this technical problem, the object of the invention is a polymer strapping tape for tying one or more objects, containing:

a) up to about 90 wt.% polyester;

b) from about 1 to about 5 wt.% polyolefin;

c) from about 5 to about 10 wt.% fibrous material.

In the case of the above components a) -c) of the polymer strapping tape, we are talking about the main components, to which, in circumstances, unavoidable contamination or other components may be added, which, however, amount to no more than 1 wt.% Of the corresponding polymer strapping tape ( in dry condition).

In this case, the indication of the word “approximately” when indicating weight indicates that the determination of the individual components is carried out using differential scanning calorimetry (DSC). In relation to the above method, its use, and expression, reference is made to the textbook "Differntial Scanning Calorimetry - An Introduction for Practioners" by Hene, Hamminger and Flammersheim (Springer Berlin, 1966). In any case, differential scanning caorimetry is associated with errors caused by the system in determining the corresponding weight fraction, which are expressed by the word “approximately”.

In the case of a polymer strapping tape according to the invention, it is always a matter of so-called separate strips, that is, the corresponding polymer strapping tape is directly extruded with the required width and thickness of the material, and is not made, for example, by longitudinal cutting of the film. Thus, the polymer strapping tape according to the invention is made in the form of a tape of a separate strip. In this regard, the polymer strapping tape or single strip tape typically has a material width or width of 2 mm to 40 mm, and preferably a material width of 5 mm to 40 mm. In addition, the thickness of the material lies in the range from 0.1 mm to 3 mm and, preferably, the thickness of the material is from 0.3 mm to 2 mm. In most cases, in this case, a material thickness of about 1.2 mm is sufficient.

The fibers used in the fibrous material typically have a higher melting point than components a) and b). This means that the melting temperature of the fibers of the fibrous material is generally substantially higher than 300 ° C. Thus, it is ensured that even at elevated application temperatures when using the polymer strapping tape according to the invention, the fibers retain their structure and, in particular, are able to take tensile forces in the longitudinal direction of the polymer strapping tape.

Typically, the fibers have a thin and flexible structure with respect to length. The fibers used in the polymer strapping tape in accordance with the invention mainly take (longitudinal) tensile forces and, therefore, serve to increase the strength of the thus produced polymer strapping tape in its longitudinal direction. In this case, it is possible to achieve tensile strengths of at least about 30 kN / cm ² , in particular even 40 kN / cm ² . The fibers of the fibrous material typically have a length of not more than 20 mm, in particular 10 mm. Their diameter can range up to 1 mm, preferably 0.5 mm or less. In most cases, the diameter is not more than 0.1 mm, under circumstances not more than 0.2 mm.

Thus, the fibers can be easily incorporated into the polymer material and are also mobile, at least during the manufacturing process. This is true even when the polymeric material or the single strips according to the invention representing the strips of single strips have a material thickness of only about 1 to 2 mm. The already mentioned mobility of the fibers is necessary, since the extruded polymer strapping tape or the polymeric material of the strapping tape is stretched, resulting in not only molecular orientation in the polymer or polymer matrix, but also the orientation of the fibers of the fibrous material. In this case, both molecular orientation and fiber orientation are carried out in the longitudinal direction of the polymer strapping tape according to the invention in order to achieve the strengths shown and indicated.

In conjunction with the fact that the polymer matrix designed to receive the fibrous material contains mainly polyester and optionally a polyolefin, a polymer strapping tape is provided that not only has significant strength parameters in the longitudinal direction, but also has no tendency to untwist or stress splitting in the longitudinal direction. This can be explained mainly by the fact that due to the additional use of a polyolefin with a specified weight percentage of from about 1 to about 5 wt.%, Polymer chains are connected to each other (in the transverse direction), using mainly up to 90 wt.% Of polyester.

Such a connection of the individual chains of the polyester is already achieved due to the low weight content of the polyolefin used, comprising approximately 1 wt.%. The more polyolefin is used, the more pronounced this effect is, however, however, approximately 5% by weight of the polyolefin content means an upper limit. That is, a higher weight content of the polyolefin in this case leads to a significant decrease in the strength achieved by the polyester component.

For this reason, the content of polyolefins cannot constantly increase, or the high weight content of the polyolefin can be compensated within the framework of the invention only due to the fact that the additionally introduced fibrous material not only compensates for the reduced strength due to the use of the polyolefin, but even excessively compensates for it. Therefore, the polymer strapping tape according to the invention combines the advantage of the known polyester / polyolefin polymer tape in that splitting is prevented and at the same time, the strength is even increased compared to a conventional tape.

Thus, the polymer strapping tape according to the invention is ideal for using recyclable materials. In fact, recyclable material originating in part from PET bottles that can be recycled into so-called PET flakes, as described in principle in US Pat. No. 4,831,088. Such PET flakes usually consist mainly of polyester and partly of one or more polyolefins. In the framework of the invention, it is preferable to use such PET flakes for the manufacture of a polymer strapping tape, and depending on the final composition of the PET flakes, additives to the extrudable material and, in particular, within the framework of the invention, the fibrous material c) in that concentrations, which are thus mixed with the material to be extruded before extrusion. The ranges of the weight content of the fibrous material from about 5 to about 10% by weight stipulated under characteristic c) are established as a result of the fact that a certain fiber content is additionally necessary in order to allow a substantial increase in strength, as described mainly in the longitudinal direction . In this case, it was found that the improvements typically reach already at 5 wt.% The content of the fibrous material.

Of course, the strength cannot be increased infinitely, since otherwise the fibers embedded in the polymer matrix cannot easily be aligned in the longitudinal direction of the polymer strapping tape during the forced stretching process. In this case, the upper limit of about 10 wt.% Of the fibrous material was determined as still suitable, since with this weight content the necessary mobility of the individual fibers is still provided for the described tensile process.

In a preferred embodiment of the invention, the polyester content is from about 85 to about 90% by weight, in particular about 90% by weight. A higher polyester content is not necessary due to the addition of fibrous material, moreover, the added fibers provide a significant increase in the strength of the polyester starting material even in the presence of polyolefins.

The polyolefin used may be polyethylene, polypropylene, as well as combinations thereof. It is fundamentally possible to use comparable polyolefins, as they are described in detail in the framework of the application WO 03/0987200 A1, referred to above.

As the fibrous material, various materials can be used. So, in principle, it is possible to use natural fibers. Such natural fibers include, but are not limited to, plant fibers, which can be used within the scope of the invention. Alternative or additionally of particular importance are mineral fibers, which, for example, are used in the construction industry in fiber gypsum. Such mineral fibers mean fibers without organically bound carbon.

Alternatively or in addition to natural fibers, chemical fibers that were formerly called artificial fibers can be used as the fibrous material. In this case, particularly favorably proved, in particular, cellulose fibers or rubber fibers made from natural polymers. Along with such fibers from natural polymers, it is also possible to use fibers from synthetic polymers, for example polyamide fibers, aramid fibers, polytetrafluoroethylene fibers, polyvinyl chloride fibers, etc. A prerequisite for these chemical fibers or fibers of the fibrous material as a whole is that they have a higher melting point than the polymer strapping tape components a) and b) and in most cases their melting point is over 300 ° C.

Based on these requirements, particularly preferably, industrially manufactured inorganic fibers are used. This is, for example, fiberglass, basalt fibers, carbon fibers or the like. It is also possible to use ceramic fibers. Moreover, in all these cases it is understood that the fibrous material can mainly consist or be composed by a combination of the previously described and separately characterized fibers.

The subject of the invention is also a method of manufacturing a polymer strapping tape, which is described in detail above. The corresponding method is explained in more detail in paragraph 10.

The polymer strapping tape according to the invention is not only characterized by increased strength compared to the prior art, but also by increased temperature stability. An improved relaxation profile is also observed. This should be understood as the property of polymer strapping tapes to accept a steady state with a reduced voltage. In fact, for example, in the case of polymeric polyester strapping tapes, it is observed that they, after the strapping process, lose about 30% of their voltage during the first five days at room temperature. Elevated temperatures lead to the fact that the described voltage reduction of 30% occurs over a period of time even less than five days.

This means that the mechanical stress in the described exemplary case decreases with constant tension over time, namely in the case of a polyester polymer tape, by about 30%. In the framework of the invention, it was found that by adding a polyolefin and, in particular, using a fibrous material in an amount of from about 5 to about 10 wt.%, A positive effect on the relaxation behavior. In the case of the polymer strapping tape according to the invention, a temporary decrease in mechanical stress is observed under constant tension, which is substantially less than 30%, preferably only 20% or less, in particular only 10% or less. This means that with constant tension, the stress in accordance with a particularly preferred embodiment is reduced only by a maximum of 10%. As a result of this, the objects to be tied up no longer need such a high tension on the binding tape as previously. As a result, it is possible to use strapping machines with smaller dimensions and, of course, less energy is required.

In the case of objects to be tied, we are talking mainly, for example, of banks, blocks, bales (bales), etc., which can be fixed on tension plates. It goes without saying that, if necessary, other objects can also be tied with a polymer strapping tape according to the invention.

Finally, it has proven useful to provide embossed tape according to the invention with embossed structures on at least one surface of the tape. In this case, we can talk about regular structures, such as, for example, a rhombus, etc. Thus, the contact surface of the polymer strapping tape decreases during transportation, for example, in the guide channel of the tape, so that friction is reduced. At the same time, the formation of a kind of “air cushion” is observed, which further simplifies and improves the transportation of the polymer strapping tape according to the invention through the corresponding guide channel of the tape. In addition, due to such knocking or extrusion, a positive influence on the special properties of the corresponding polymer strapping tape can be deliberately exerted. This applies, in particular, to the stiffness of the tape, so that when such knockouts or extrusions are realized, the cross section of the tape can be reduced. This leads to lower manufacturing costs. The described embossments or extrusions can be applied using one or more embossing rolls, as will be explained in more detail below.

On the other hand, in the polymer strapping tape, synergistic effects are generally observed between extrusions, on the one hand, and a fibrous material or a combination of polyester and polyolefin, on the other hand. Since the polyester / polyolefin combination already leads to increased strength and to the fact that the so-made strapping tape, in particular the single-strip tape, does not split or unwind in the longitudinal direction (see application WO 03/087200 A1).

By introducing fibers or fibrous material in the indicated amount by weight, it is further achieved that, on the one hand, the polymer strapping tape made in this way can be used in applications with elevated temperature and, on the other hand, the fibers retain their structure, which, in accordance with the invention also relates to the entire polymer strapping tape as a whole. This means that the polymer strapping tape is characterized by high dimensional stability even at high temperatures. As a result of this, an impeccable thermal connection between the ends of the strapping tape according to the invention is possible, namely over a full area, so that increased strength is observed in this place compared to the prior art. In addition, the increased dimensional stability in comparison with the prior art significantly reduces the possibility of damage to the polymer strapping tape during use.

Finally, embossing has a beneficial effect on the transportation of the polymer strapping tape through the strapping band channel, on the one hand, and allows, on the other hand, additionally reducing the thickness of the material compared to strapping belts without embossing. This means that both embossing and the introduced fibrous material increase the strength of the polymer strapping tape according to the invention with the consequent possibility of reducing the overall thickness of the material. Thus, there is a saving in the raw materials used, the value of which lies in the double-digit range.

The embossing process is carried out at the end of the manufacturing process of the polymer strapping tape according to the invention, when the introduced fibers are no longer mobile or weakly mobile inside the polymer material. As a result of this, an additional embossing step provides an additional and desirable compaction of the fibers within the polymer strapping tape. Due to this, an additional increase in strength is achieved.

In the framework of the following embodiment, the installation for manufacturing the polymer strapping tape according to the invention is explained in more detail. A single figure shows a device for manufacturing a polymer strapping tape for tying one or more objects.

In the drawing. 1 shows, first of all, an extrusion device 1, which is equipped with an extruder screw 2 and an extruder feed hopper 3. In the feed hopper 3 of the extruder is a stock of raw materials that is fed to the screw 2 of the extruder, for the manufacture of polymer strapping tape 4, which extends from the outlet 2 of the extruder. Therefore, the feed hopper 3 of the extruder contains an extrudable mixture.

After extrusion of the polymer strapping tape 4 on the exit side of the screw of the extruder 2, it first passes through the water bath 5. After the water bath 5, a first stretching device 6 and a second stretching device 7 are provided. The second stretching device 7 is also equipped with an oven 8, through which the polymer strapping tape 4 are omitted in the second stretching process. With regard to stretching, the rule applies according to which the polymer strapping tape leaving the screw 2 of the extruder is stretched in compliance with a draw ratio from 1: 2 to 1: 5, in particular 1: 4. This means that the polymer strapping tape 4 leaving the screw 2 of the extruder is stretched in the first or in the second stretching device 6, 7 by an amount from two to five times the length.

The furnace 8 in the second stretching device 7 ensures that the molecular orientation of the polymer chains achieved by stretching remains unchanged, and in the same way, the alignment of the fibers does not disappear or unravels after the stretching process is completed. After passing through both stretching devices 6, 7, an additional subsequent embossing of the polymer strapping tape 4 is carried out. An embossing device 9 is provided for this, which is equipped with a first embossing roller 10 and an opposing counter-pressure roll or counter-pressure roller 11 interacting with the embossing roller 10.

Using the embossing device 9, the polymer strapping tape 4 is provided on at least one surface of the tape in the longitudinal direction with an extruded or protruding embossing. To this end, the embossing roll 10 is heated to a temperature above ambient temperature of approximately 50 ° C or 60 ° C and has an appropriate surface contour depending on the desired embossing. Thus, it is possible not only to significantly reduce the contact surface of the polymer strapping tape with, for example, the guide channel of the tape in relation to the fit over a full area and, consequently, also reduce friction, but it is also possible to use the previously mentioned “air cushion effect” during polymer transportation strapping tape. It should be added that the applied embossments in the longitudinal direction of the polymer strapping tape generally increase its rigidity. Due to this, with the same stiffness, it is possible to reduce the cross section of the tape, which means material savings.

The polymer strapping tape 4 is directly made using a suitable device, that is, it is provided with a width of from about 5 mm to about 40 mm. The thickness of the material is about 0.1-0.3 mm. Alternative to this, however, it is also possible to work with the material of the polymer strapping tape on the exit side of the extrusion device 1 of the described specification. The material of the polymer strapping tape can be cut in front of the stretching devices 6, 7 in the longitudinal direction into the polymer strapping tape 4, which, however, is not shown.

Claims (10)

1. Polymeric strapping tape (4) for tying one or more objects, containing:
a) up to about 90 weight. % polyester;
b) from about 1 to about 5 weight. % polyolefin; and
c) from about 5 to about 10 weight. % fibrous material. 2. Polymer strapping tape (4) according to claim 1, characterized in that the fibrous material c) has a higher melting temperature compared to components a) and b). 3. Polymeric strapping tape (4) according to claim 1, characterized in that the polyester content a) is from about 85 to 90 weight. % and, in particular, approximately 90 weight. % 4. Polymeric strapping tape (4) according to claim 1, characterized in that the polyolefin is polyethylene, polypropylene or a combination thereof. 5. The polymer strapping tape (4) according to claim 1, characterized in that the fibrous material c) consists of fibers with a length of not more than 20 mm and, in particular, 10 mm. 6. Polymeric strapping tape (4) according to claim 1, characterized in that natural fibers, in particular vegetable and / or mineral fibers, are used as the fibrous material c). 7. Polymeric strapping tape (4) according to claim 1, characterized in that chemical fibers are used as the fibrous material c), in particular cellulose fibers or rubber fibers made from natural polymers. 8. Polymer strapping tape (4) according to claim 1, characterized in that the fibrous material c) contains inorganic fibers, for example glass fibers, basalt fibers, carbon fibers, ceramic fibers or the like. 9. Polymer strapping tape (4) according to any one of paragraphs. 1-8, characterized in that the fibrous material c) consists of a combination of fibers in accordance with paragraphs. 6-8. 10. A method of manufacturing a polymer strapping tape, in particular, according to any one of paragraphs. 1-9, in which components a) -c) are mixed with each other and coextruded, then the resulting polymer strapping tape (4) or the strapping strand polymer material is stretched, while the strapping strand polymer (4) or strapping strand polymer material is stretched subject to a draw ratio of 1: 2 to 1: 5 and then, if necessary, embossed on one of its surfaces.

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